1. Field of the Invention
The present invention generally relates to electronic devices. More particularly, the present invention relates to an electronic device that makes it easy to assemble members disposed in a housing.
2. Description of the Related Art
Typically, in cases in which a plate member, such as a substrate, is disposed in a housing, for example, in the case of an electronic device, various substrate securing methods are conceived (e.g., Japanese Unexamined Patent Application Publication Nos. 09-260871 and 2007-48914).
For example, Japanese Unexamined Patent Application Publication No. 09-260871 discloses a method for positioning and supporting a wiring substrate by directly providing a protrusion on the bottom plate of a device main unit and fitting the protrusion into a hole provided at an approximate center of the wiring substrate. Japanese Unexamined Patent Application Publication No. 2004-349297 discloses a mechanism in which the positioning of a jack substrate is performs by a rear panel and a protrusion.
In such a device in which a plate member (a first member) is disposed in a housing, a second member may be secured to a surface of the first member, the surface being a reverse side viewed from the worker (hereinafter, the surface may be referred to as a “back surface”) when the first member is disposed in the housing.
FIG. 1 is a sectional view showing an example of the configuration of an electronic device having such an internal structure.
In FIG. 1, an electronic device 10 has a substrate 11 in its housing 20. An IC (integrated circuit) 12 is provided on a surface of the substrate 11, the surface being an upper side thereof in FIG. 1. A reinforcing plate 13 is attached to a position that lies at a lower surface (in FIG. 1) of the substrate 11 and that corresponds to the IC 12, so as to prevent the substrate 11 from bending that puts a load on contacts (terminals) of the IC 12, when the housing 20 is vibrated or is given a shock. A surface of the reinforcing plate 13, the surface being adjacent to the substrate 11, has mold portions 14 (14A to 14D) so as to prevent damage to the substrate 11.
A heat sink 15 is attached to an upper surface (in FIG. 1) of the IC 12 in order to release heat generated by the IC 12. The heat sink 15 is secured to the substrate 11 by heat-sink screws 16A and 16B. The heat-sink screws 16A and 16B also secure the reinforcing plate 13 through the substrate 11. The substrate 11 to which the heat sink 15 and the reinforcing plate 13 are secured is secured to substrate attachment supports 21A and 21B of the housing 20 by substrate screws 22A and 22B, respectively.
When a second substrate is secured to a predetermined position at the back surface of a first member rather than to a housing, as described above, the position of the first member and the position of the second member are generally aligned with each other. In this case, however, it is difficult to use the methods disclosed in Japanese Unexamined Patent Application Publication Nos. 09-260871 and 2004-349297, since these are methods for performing positioning between a substrate and a housing.
In particular, when a first member is placed on a second member that is smaller than the first member and the second member is hidden and made invisible by the first member, it is difficult to accurately control the relative position between the first member and the second member and it is thus difficult to accurately secure the second member to a predetermined position at the back surface of the first substrate.
In such a case, a method is conceivable in which, before the first member is disposed in the housing, the first member is turned upside down so that the back surface becomes the obverse surface and the second member is attached thereto. However, changing the working surface, for example, from the obverse surface to the back surface by reversing the first member in such a manner not only makes the work complicated but also can cause forgetting to attach the second member and cause damage to the first member during the change of the working surface. Thus, such a method is not desirable.
Assembly in such a case has been typically performed using, for example, a predetermined jig 30, as shown in FIGS. 2A and 2B. As shown in FIG. 2A, the jig 30 has reinforcing-plate positioning pins 31A and 31B for placing a reinforcing plate 13 at a predetermined position and substrate positioning pins 32A and 32B for placing the substrate 11 at a predetermined position.
As shown in FIG. 2A, a worker places the reinforcing plate 13 on the jig 13 so that the reinforcing-plate positioning pints 31A and 31B are inserted into reinforcing-plate positioning holes 41A and 41B provided in the reinforcing plate 13. Next, as shown in FIG. 2B, the worker places the substrate 11 on the jig 30 so that the substrate positioning pins 32A and 32B are inserted into substrate positioning holes 42A and 42B provided in the substrate 11. In addition, the worker places the heat sink 15 on the IC 12 provided on the substrate 11 and secures the heat sink 15 to the substrate 11 by using the heat-sink screws 16A and 16B. At this point, as shown in FIG. 2C, the reinforcing plate 13 that is situated below the IC 12 at the reverse side of the substrate 11 is also secured to the heat-sink screws 16A and 16B that penetrate the substrate 11.
When the substrate 11 is assembled as shown in FIG. 2C, the worker removes the jig 30 from the substrate 11, locates the housing 20 on a workbench instead of the jig 30 or moves the assembled substrate 11 to a housing-assembly line, and disposes the substrate 11 at a predetermined position in the housing 20 by using the substrate screws 22A and 22B. That is, the worker places the substrate 11 on the housing 20 so that the substrate positioning holes 42A and 42B, provided in the substrate 11, are positioned above the substrate positioning pins 32A and 32B, secures the substrate 11 to the substrate positioning pin 32A by screwing the substrate screw 22A into the substrate positioning hole 42A from the upper surface of the substrate 11, and also secures the substrate 11 to the substrate positioning pin 32B by screwing the substrate screw 22B into the substrate positioning hole 42B from the upper surface of the substrate 11.
Japanese Unexamined Patent Application Publication No. 2007-48914 discloses a configuration that is similar to the configuration shown in FIG. 1. In the disclosed configuration, a heat releasing plate is disposed below a heat releasing sheet provided on the lower surface of an IC, long screws are inserted into a bottom chassis from the lower surface thereof toward the heat releasing plate, ends of the long screws are in contact with the lower surface of the heat releasing plate, and position-alignment depressions into which the ends of the long screws are inserted are formed in the lower surface of the heat releasing plate.
For example, although no specific description has been given, some methods are conceivable. For example, the heat releasing plate is placed on a workbench upside down relative to that of the heat releasing plate shown in FIG. 3 in Japanese Unexamined Patent Application Publication No. 2007-48914, the bottom chassis is placed over the heat releasing plate upside down relative to that of the bottom chassis shown in FIG. 3 in Publication No. 2007-48914, the heat releasing plate is secured to the bottom chassis by screwing the long screws from the lower surface of the bottom chassis in FIG. 3 in Publication No. 2007-48914 (i.e., the upper surface thereof, in practice), the resulting structure is then turned upside down, and the substrate is secured to the bottom chassis, as in FIG. 1 in Publication No. 2007-48914. Alternatively, the heat releasing plate is first placed on the bottom chassis, the substrate is placed thereon and is secured thereto, the resulting structure is then turned upside down, and the heat releasing plate is secured to the bottom chassis from the lower surface of the bottom chassis in FIG. 3 in Publication No. 2007-48914 (i.e., the upper surface thereof, in practice).